Eco-friendly and Practical Synthesis of 3-Aminopyrazoles in Water

Abstract:

We present a protocol for the synthesis of 3-aminopyrazoles through an eco-friendly cyclocondensation reaction of α-oxo ketene-N, S-acetals with hydrazine hydrates. The reaction runs by using H2O as a solvent to give access to a library of 3-aminopyrazole derivatives (25 examples) under mild and operationally simple conditions. In this study, the green synthesis method showed various fascinating advantages, such as good scale-up performance, good Eco-scale value (89 points), and reusable aqueous medium. 3-aminopyrazoles were further confirmed by X-ray crystallographic analysis, and a reasonable reaction mechanism was proposed.